Piston ring



Nov. 13, 1923. 1,691,518

E. J. HALL PISTON RING Filed Sept. 22, 1925 2 Sheets-Sheet 1 HHHHIHIIIIIIIIIN Y i Xa =5 &', B '9' (II 1 L Z=8--- Patented Nov. 13 1928 UNITED STATES,

I 1,691,518 PATENT lorries.

J. HALL, OF BERKELEY, CALII'OIBNIA.

PISTON RING.

Application filed September 22, 1925. Serial No. 57,932.

This invention relates to improvements in piston rings. p I The object of the present invention is to reduce cylinder wear to a minimum in ma 5 chinery of any type usinga piston.

Most piston rings are over-tensioned when new, so as to have sufficient tension when worn to provide an effective packing, and this overtensioning of piston rings causes undue wear v of the cylinder walls.

The primary ob ect of the present invention is to produce a one-piece piston ring which will obviate the necessity of over-tensioning piston rings, by maintaining throughout the" entire life of a piston ring a predetermined pressure per unit ofarea of its cylindrical bearing face, so thato'nly the proper and desired amountof tension is necessary in a new ring, and no undue wear will be caused by the ring when new.

A further object ofthe invention is to provide a piston ring in which the area of its cylinder wall contacting surface will, decrease with the wear of the ring, thereby causing a reduction in tension, so as to maintain a a constant predetermined relation between the "said cylinder wall contacting surface and thetension of the ring, thereby enablin the desired proper amount of pressure to e maintained at all times b the piston ring against the wall of the cylin er. 4 j

With "these and other objects inview, the invention consists in the construction and novel combination and arrangement of parts hereinafter fully described, illustrated in the accompanying drawings and pointed out in the claims'hereto appended, it being understood that various changes in the form, proportion and minor details of construction,

, 40 within the scope of the claims, may be resorted to without departing from the spirit or sacrificing any of the advantages of the invention. 1

Inthe drawings:

. Figure 1 is a side elevation of a piston rin b constructed 1n accordance with thls invention.

Figure 2 is a. transverse sectional view of the same. I o

Fig. 3 is an enlarged cross section of the ring. I

Fig. 4 is a diagram illustrating the'problem of ascertaining the angle or inclination for producing a variable bearing surface ada ted" to be reduced in area with the wear 0 the piston ring,

" Fig. 5 is a cross section of'a piston ring pro.-

form of the invention and showing a pistondecreases through wear the area of the cylinvided at each side of its cylinderi wall engaging or bearing surface with an inclined face. Fig. 6 is a slmilar view illustrating another ring composed oftwo ring sections each provided at its outerside with an inclined face.

Fig. 7 is a cross section of a piston ring provided centrally of its cylinder wall engagin face with an annular groove having inclined side walls or faces.

Fig. 8 is a cross sectional view showing a similar construction composed of two ring sections. 1 v

Fig. 9 is a sectional view or,portion of a piston provided with a piston ring showin another form of the invention having incline faces extending the entire thickness of the piston ring.

Fig. 10 is a similar view showing a piston rin having an inclined face at each side exten ing'the entire thickness of the'ring.

Referring particularly to Figs. 1 to 4 inclusive of t e drawings, 1 designates a piston ring designed to take the place of the ordinary piston ring and provided at one side with a circumferential recess 2 having an inclined side wall 3 forming an undercut at the circumference of the piston ring and extending inwardly from the cylinder wall engaging surface 4 at the outer face of the ring and providing an inward taper in the ring der wall engaging surface ofthe' ring is correspondingly reduced-so as to maintain constantly a predetermined relation between the outer cylinder wall engagin surface of the ring andthe tension thereo .This willenable pistonrings to be constructed without over tensioning the same and the piston rin may be givena predetermined tension Whi will remain substantially constant throu hout thelife of the ring so that the piston rmg 11 will be effective as a packing at all times withoutundue wear on the cylinder wall.

The 'problemof the angle of tlie undercut ina wear compensated piston ring such that as the ring is worn down the pressure per unit area; exerted by the ring on the cylinder wall will remain approximately constant is worked out with referer'i'ce to the I form ofthe invention illustrated in Figs. 1'

- to 3 inclusive of the drawings andparticularly with relation to'the diagrammatic illustratlon shown in Fig. 4. but the same formula as will be readily understood is applicable to the other forms of the invention illustrated in the drawings and hereinafter described in detail. As this may be determined mathematically, it is deemed suflicient to explain the formula'only in connection with one form of the invention, viz, that illustrated in Figs, 1 to 3 inclusive of the drawings.

The problem will be solved by designing the ring so that when the ring has been worn down a given amount the pressure per unit area will be the same as it was when the ring was' first installed. Figure 4 shows a section of a wear compensated ring-0n which all of the dimensions are known except (in). The

problem will be to find a value of m such that when the'ring is worn down so-that (y) is V practically nothing the pressure per unit area -Where exerted By the ring will be the, same as it is with the section indicated. In Figure 4 the dimensions are in 64ths.

- On page 126 of FThe Gasoline Automobile byHeldt is given the equation for a ring which is circular when normal and is of rectangular section.

S=Th e fiber stress in pounds per square me a v -E=The mddulus of elasticity of the material r= The rddius of the piston ring normal,

2 ri=oThe riadius of the ring in the cylinder" t= The thickness Since t(r .+7') is small compared with of the ring radially.-

r, 12 a change in it may be considered negligi? ble; Also the change in the value'of r-due to the wearing down of the ring will'be' small compared with 1'. Taking these thingsinto cons deration it will he found that no serious error will be introduced Equation (1-) be Wherep=pounds per square inc'lh radial pressure exerted by a rectangular ring;

"b=the cylinder "bore,

9=the angular distance ofthe point in questionto the-gap of the. ring;

Substituting S in Equation (2) in Equation (3) and multiplying and dividing. by the width'W of the ring gives,

N (r -r)wt For a rectangle Q/Ut ll 2 I '(see a hand book l (5) Where It is'the moment of inertia of the section about an axis through the center of gravity of the section and parallel'to' the axis ofth'ering. 1 Substituting (5) in (4) gives,

1 i I *wrb sin i For: a given position on the ring. is c0n'-' stant. Consequently,

Where Kis a constant." Substituting (7) vin (6) gives,

Where a: equals-w, the width of the ring in contact with the cylinder.

. Let 1,, and n refer to the section of'the ring and 1r; toits ndrmal radius when it is new and let I and 1",, refer to the same after i the ring has worn-down so that is practically zero. Then according to the original prop- TransPosing and cancelling and callng r,Iand w, v ,i a 4 I l a) h 4 I =.6662d (seej'a handbook)= 566(8) (3.5) =229 w =a constant=5 j r,=2.112(64) an arbitrary constant) an arbitrary constant an arbitrary constant gives: A 2-29 (5) (2.112(64) 2.162(64) (2.194)) (69 (2.112(64) -2..1 94(e4)) (2.162) (64) v n I Ix, =707 --(10) Now, I must beexpressed'in terms 5::

. i Substituting these values in the equation;

; The-bottom wall 5 of the groove 2 is in Consider the section (Figure 4) vto be di-.

svided into two areas A and B. For the whole section I refers to the center of gravity axis moment of inertia. 1 The line is through the center of gravity of the wholefsection.

I=L,,+I 11 Where 1,, and I are the moments of inertia of the areas A and B respectively about the axis 00.

I =I '+g -B and I =LK+f A (see a hand book) (12) Where I and 1;, refer to the moment of inertia about the center of gravit of 'B and A respectively. Substituting 812) in (11) gives:

-I'=IA+ A+I 4 9 B (13) (See a handbook) Combining Equations (l3) to (21) in elusive gives the value of 1 in terms'of as which when substituted in Equation gives:

. be solved'by formulas but the method would be extremely cumbersome; Instead m was given trial values until one was found which would satisfy the equation. The value w'=1.95 was found tosatisfy the equation.

Hence I w=1.95 64=ths of an inch, r

':v=.0304 inches.

parallelism with the inner and outer faces of the ring and the side faces 6 and 7 of the piston ring are arallel and present flat abut- .ments to thewalls of the piston groovesso that ring groove wear is reduced toa minimum.

In Fig. 5 of the drawing is illustrated another form of'the invention in which the'piston ring 8 is provided at both sides with air-- cumferental grooves 9. each having an inclined wall 10' extending inwardly. from the "outer cylinder wall engaging surfaces 11 and the inclined walls 10 form undercuts which produce an inwardly tapered outer portion in the rin adapted to compensate for the wear of the ring and maintain approximatelyconstant the pressure per unit of area exerted by the piston ring on the cylinder wall during The bottom walls 12 of the side circumferential grooves 9 are in parallelism with the inner and outer faces of the piston ring and .thefside faces'of the (piston ring are parallel.

V awing is illustrated a form of the invention in which the piston ring In Fig; 6 of the inner an outer facesof the ring.

is composed of two ring sections 13 each provided at its outer side with a circumferential groove 14- having an inclined side wall 15 forming an undercut similar to the inclined walls of the rings heretofore described. The bottom walls of the grooves 14 are in parallelism with the inher and outer faces of the piston ring sections and the side faces of the section are parallel, the innerside faces abutting and extending from the inner face ofthe rin to the outer face thereof. The abutting re ation of the rin sections throughout their entire inner side aces produces a com-' posite ring of approximately'the construtlon ofthe single piece ring illustrated'in Fig. 5 of thedrawings. 6

In Fig. 7' of the drawings is illustrated a piston rmg It? provided with a central circumferential groove 17 having'inclined side walls 18 forming undercuts and extending inwardly from the outer surfaces 19 of the'side portions 20 of the ring 16. .These side portions .are tapered inwardly and com ensate for the wear ofthe iston ring andt e ring presents parallel si e' faces to the walls of the ring groove of thepiston. The bottom iivzall 21'of the central circumferential groove 1s in In, Fig. 8 of the drawings is illustrated a sectionalpiston ring composedvof two sections 22 formed by dividmg the ring centrally ofthe groove 23. The side walls 24 of the groove 23-are inclined and extend inwardly from the outer surfaces of the ringsections and produce tapered portions in the arallelism or concentric with the grooves of a piston.'

said sections to compensatelfor the wear of the pistonring. The outer side-faces of the sections are parallel and extend from ,the

inner to the outer'face of the piston ring and present flat-surfaces to the walls of the ring In Fig. 9 of the drawings illustfateda piston'ring 25 having an inclined side face .26 extending inwardly from the outer face of the ring to the inner face thereof. The other side face 27 of the piston ring is perpendicular to the axis of. the piston-and presents a flat surface tothe wall 28 of the ring-groove 29 of the piston 30. The other wall 31 of the ring groove of the piston is inclined in substantially parallelism with the inclined side face 26 of thepiston ring 25.

In Figofthe drawing is illustrated a piston ring 32 having both of its'side faces 33 inclined to provide a double undercut to the ring. The inclined side faces extend inwardly from the outer face 34 of the ring 32 to the inner face 35 thereof. In both the rings and 32 a continuous' taper is formed in the ring from the outer faceto the inner face thereoff Also the angleor curve of the undercut may be plotted to take care of wearon the cylinder Walls so that the taper of the 'ring will-be such that both the Wear of the I inderswall engagin compression ring and the wear of the cylinde'r walls will be compensated for.-

.What is claimed is 1. A wear compensated piston ring having an outer cylinder wall engaging surface, an

undercut therefrom to provide an inward t-aperadapted as the ring wears in thickness to simultaneously reduce the area of the cylsurface,'the angle of the undercut being suc as to maintain approximately constant the pressure per unit area exerted by the ring on'nthe cylinder wall throughout thelife of the ring.

2; A wear compensated piston ring having an outer cylinder wall engaging surface, and

provided thereat with a circumferential groove forming an undercut and having .an inclined side. wall, said inclined wall forming an inward taper in the ring from the cylinder wall engaging surface and the angle of the wall being such as .to maintain approximately constant thepressure per unit .area exerted by the ring onthecylinder wall throughout the life of the ring.

compensated piston ring pro-' vided in groove having inclined side walls extending inwardly from the outer surface of the piston,

its outer facewith a circumferentiah ring andforming undercuts," the sidewalls of the groove being inclinedand the angle of the side walls of the said groove bein such asto maintain constant, approximate y, the ressure per unit area exerted by the ringon the cylinder wall throughout the lifeof the ring. I

4. A wear compensated piston ring pro-- vided in its outer face with a circumferential groove having'inclined side walls extending inwardly from the outer surfaceof the piston 1 ring and'formin undercuts, the side walls I of the groove. being inclined and the angle of the side walls of the saidrgroove being such as to maintain approximately constant the pressure per unit-area exerted by thefromthe inner face of the ring to the outer thereby maintaining an approximately constant uniform rin tension per unit of areav l engaging surface of the life of the of the cylinderw compression ring throughout the ring. v

6, A compensating ring for cylinders hav ing a tapered portion undercut at. an angle the'angle of the undercut being such as to proportionately reduce the axial width of the tapered" portion simultaneously with the diametrical reduction in thickness through wear ofthe ring of the said tapered portion I to maintain approximately contant the ring sion-ring a W A I .7. Themethod of maintaining approximately uniform ring tension per unit of area tension throughout the life of the compres- 'of the cylinder wall engaging surface of compression rings consisting in undercutting thet ring to produce aninward taper and. proportionately reducing the axial .width of the tapered ortionsimultaneously withthe re-- duction v wear in the diametrical' thickness of the said tapered portion; v I

' ELBERT .i. HALL;- 

